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Comparative statistics and origin of triple and quadruple stars
The statistics of catalogued quadruple stars consisting of two binaries(hierarchy 2 + 2), is studied in comparison with triple stars, withrespective sample sizes of 81 and 724. Seven representative quadruplesystems are discussed in greater detail. The main conclusions are asfollows. (i) Quadruple systems of ? Lyr type with similar massesand inner periods are common, in 42 per cent of the sample the outermass ratio is above 0.5 and the inner periods differ by less than 10times. (ii) The distributions of the inner periods in triple andquadruple stars are similar and bimodal. The inner mass ratios do notcorrelate with the inner periods. (iii) The statistics of outer periodsand mass ratios in triples and quadruples are different. The medianouter mass ratio in triples is 0.39 independently of the outer period,which has a smooth distribution. In contrast, the outer periods of 25per cent quadruples concentrate in the narrow range from 10 to 100yr,the outer mass ratios of these tight quadruples are above 0.6 and theirtwo inner periods are similar to each other. (iv) The outer and innermass ratios in triple and quadruple stars are not mutually correlated.In 13 per cent of quadruples both inner mass ratios are above 0.85(double twins). (v) The inner and outer orbital angular momenta andperiods in triple and quadruple systems with inner periods above 30dshow some correlation, the ratio of outer-to-inner periods is mostlycomprised between 5 and 104. In the systems with small periodratios the directions of the orbital spins are correlated, while in thesystems with large ratios they are not. The properties of multiple starsdo not correspond to the products of dynamical decay of small clusters,hence the N-body dynamics is not the dominant process of theirformation. On the other hand, rotationally driven (cascade)fragmentation possibly followed by migration of inner and/or outerorbits to shorter periods is a promising scenario to explain the originof triple and quadruple stars.
| The long-period companions of multiple stars tend to have moderate eccentricities
We examined the statistics of an angle gamma between the radius vectorof a visual companion of a multiple star and the vector of its apparentrelative motion in the system. Its distribution f(gamma ) is related tothe orbital eccentricity distribution in the investigated sample. Wefound that for the wide physical subsystems of the 174 objects from theMultiple Star Catalogue f(gamma ) is bell-shaped. The Monte-Carlosimulations have shown that our f(gamma ) corresponds to the populationof the moderate-eccentricity orbits and is not compatible with thelinear distribution f(e)=2e which follows from stellar dynamics andseems to hold for wide binaries. This points to the absence of highlyelongated orbits among the outer subsystems of multiple stars. Theconstraint of dynamical stability of triple systems is not sufficient toexplain the ``rounded-off'' outer orbits; instead, we speculate that itcan result from the angular momentum exchange in multiple systems duringtheir early evolution.
| Mining in the HIPPARCOS raw data
The Hipparcos solutions flagged as unreliable after the completion ofthe standard data processing have been systematically revisited in thelight of additional information, primarily related to theirmultiplicity. In many cases improved solutions have been obtained,yielding at the same time an Hipparcos based separation and positionangle and a better astrometric solution for the system. The principlesapplied in this reprocessing are explained and more than a hundred newsolutions with absolute and relative astrometry are presented anddiscussed. Tables 1 to 7 are also available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Maximum separations among cataloged binaries
The paper classifies many of the widest common-motion binaries listed inthe Aitken catalog and list 72 physical pairs with known photoelectricphotometry, 31 physical pairs without good photometry, and 27 opticalpairs. As a function of primary types, the physical systems have upperlimits to their separations that are exceeded by some of the opticalpairs. The fact that optical pairs occur with larger separations impliesthat the limits are real ones and not just catalog limitations. Thoselimits (in AU) are expressed by 2500 M1 exp 1.54 for B5-KO main-sequenceprimaries. The same limits hold for the Trapezium and hierarchicalsystems studied previously.
| Visual multiples. VII - MK classifications
Classifications are given for 865 components of visual multiples; theyshow no systematic differences from the MK system, and the random errorsare one subclass in type and two-thirds of a luminosity class. It isfound that at least 1% of the F-type IV and V stars are weak-lined, 32%of the A4-F1 IV and V stars are Am, and 5% of the A0-A3 IV and V starsare early-type Am. Attention is called to the large fraction (55%) ofthe A3-A9 III-V stars that are of luminosity classes III or IV, unlikethe percentage (16%) at neighboring types.
| Photographic measures of double stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1..357T&db_key=AST
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